A group of mayors from border towns in the US state of Texas has called for sections of the Rio Grande to be dammed as a deterrent to illegal immigration.

The mayors want to deepen and widen the natural border with Mexico through a series of low dams or weirs across the desert flood plain.

Tens of thousands of people cross the river border illegally every month.

Critics say more people will die trying to get over the border if the river-crossing is made more dangerous.

The Rio Grande, or the Rio Bravo del Norte as it is called in Mexico, forms the border between the US state of Texas and Mexico.

It is a popular point of entry for the many thousands of illegal immigrants hoping to cross over into the US.

Many people in the border regions are unhappy about the growth of illegal immigration.

Part of the Bush administration's response has been to start the construction of hundreds of kilometres of security fence along the border, backed up by patrols and surveillance cameras.

Cost-effective

But now a group of Texan mayors, business leaders and county judges feel the approach is misguided.

They say the key to stopping illegal immigration - at least in Texas - is the Rio Grande.

They propose damming the river along several important sections in the flood plain to widen and deepen the river, making it too hazardous to cross.

Technology is the way to sincerely secure the border

Chad FosterMayor of Eagle Pass

They believe the measure, when taken in conjunction with improved surveillance, is much more cost-effective than the fence.

"We're only going to have one chance to secure the border and we feel that in this modern age, technology is the way to sincerely secure the border," says the group's leader, Chad Foster, the mayor of Eagle Pass.

"The fence... is going to convey a false sense of security, and the border patrol has said it will only slow down an illegal entry by three to four minutes," he added.

Some border towns on the Mexican side of the Rio Grande are also in favour of the measure, reports suggest, because they believe it will help to increase the region's water supply.

But critics of the scheme say that it will do nothing to reduce the number of people prepared to risk everything in search of a better life in the north, and a more dangerous river-crossing will simply mean that more of them will die in the attempt.